The turbine blades of the high-pressure turbine belong to the most highly loaded components of a gas turbine or of an aircraft engine. At the same time, even slight damage or deviations from their respective original shape of the high-pressure turbine blades have a not inconsiderable influence on the efficiency of the gas turbine, which ultimately affects the fuel consumption.
Because of the particular loading, the high-pressure turbine blades are regularly overhauled or, if this is not possible, replaced by new parts. For this purpose, the gas turbine has to be broken down, at least to such an extent that the turbine blades of the high-pressure turbine can be removed. The previously removed turbine blades can be mounted again following a possibly time-consuming overhaul. As an alternative thereto, other turbine blades already overhauled in another way or new parts can be mounted, in order to keep the necessary maintenance time for the gas turbine as short as possible. The latter is important in particular in aircraft engines.
Turbine blades regularly have a unique serial number. For turbine blades of aircraft engines, this is necessary because of approval requirements. The serial numbers are arranged on the root of the turbine blades, with which the blades are fixed to the blade carrier of the engine, in order to avoid their coming directly into contact with the hot gas stream and being made unrecognizable thereby.
The disadvantage with the positioning of the serial number on the root of a turbine blade is that the serial numbers are no longer visible following the insertion of the turbine blades. Thus, in the case of a completely mounted gas turbine or a completely mounted aircraft engine, it is not possible to check the serial number of an individual engine blade. In order to determine the serial number of a specific engine blade, according to the prior art a virtually complete breakdown of the entire gas turbine is instead necessary.
In particular when overhauled turbine blades are used, even when checking of the turbine blades is carried out before and after the mounting, even shortly after the commissioning of the reassembled gas turbine, to some extent even after a first test run, an at least slightly reduced efficiency can be established, which ultimately results in an increased fuel consumption in the use of the gas turbine. Even if a correspondingly reduced efficiency frequently does not justify any renewed disassembly of the gas turbine, it may be wished, for many reasons, to clearly identify the component causing the loss of efficiency of the gas turbine. For example, appropriate identification is desirable in order to be able to make possible compensation claims on the manufacturer of a clearly identifiable component or on the maintenance facility which has overhauled the questionable component.
If a turbine blade of the high-pressure turbine of the aircraft engine is identified as a probable cause of the loss of efficiency, it is impossible in the prior art, however, to identify the turbine blade in question clearly, for example by using its serial number, without a virtually complete breakdown of the gas turbine. As a result, the origin of the turbine blade from a manufacturer or repair facility cannot readily be clarified.
The documents DE 10 2011 114 541 A1, EP 1 609 957 A2, US 2013/0 113 915 A1, US 2014/0 188 423 A1 or WO 2015/130 870 A1—disclose diverse methods, including partially automated methods, for the boroscopic inspection of turbine blades or other components in a completely mounted aircraft engine. However, a possible way of identifying the turbine blades visible by the boroscope is not described.
The documents DE 10 2011 103 003 A1 and U.S. Pat. No. 9,016,560 B2 disclose automated optical methods for checking disassembled engine blades, wherein the serial numbers provided on the blade root can be configured to be machine-readable.